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It seems to me that he is discribing a species that has altered slightly in some way, possibly through epigenetics or other to proceed where the same species of previous generations did not change, had no need to change.
..... I assume what happens is that over a long enough period, related groups become incapable of interbreeding because they are prevented from interbreeding through isolation, or some physical change that makes it impossible. Then over a long period of time, their genes diverge sufficiently that interbreeding becomes impossible. At that point, you have a new species.Are horses and donkeys different species? I tend to think they are. They can interbreed to produce a mule, but there will never be a species called "mules". Mules, are incapable of breeding.
All populations of organisms have some variety and new variations enter into the population all the time through mutation. If there is no pressure from the environment that makes one variation significantly different from another, then there will be no change in the average individual in the population over time. If something in the environment makes it so that one or two variations are significantly different (and better able to survive), then over time the average individual in a population will change accordingly.Small changes in variation can build up over time.
Quote from: echochartruse on 26/03/2010 01:55:42Was it just the same species doing adaptaions to the surrounding environment? Did an entirely new species come from another species?Essentially yes, but you shouldn't get hung up on the idea of different species. "Species" are, after all, just labels that humans put on different things.Quote from: echochartruse on 26/03/2010 01:55:42did the kangaroo climb a tree to become a possum then decide to climb down and becoem a rock wallaby? then why didnt they all become possums? There was once an ancestor of all these animals. Some of these (for whatever reason) spent more time in the trees - this population were then subject to the selection pressure of arborial life, and eventually became the species we now call the possum. Other populations of this ancestor species moved into other environments, and different selective pressures acted.Quote from: echochartruse on 26/03/2010 01:55:42Survival of the fittest, why didnt they all become one species what changed some to be another species, dont they know humans are top of the evolution chain.This is due to the fact that several different things can be the "fittest" for different ways of life in the same area - each one specialising towards a different way of life.Humans are not special - we're not top of the evolution chain - every extant species is the pinnacle of evolution.
Was it just the same species doing adaptaions to the surrounding environment? Did an entirely new species come from another species?
did the kangaroo climb a tree to become a possum then decide to climb down and becoem a rock wallaby? then why didnt they all become possums?
Survival of the fittest, why didnt they all become one species what changed some to be another species, dont they know humans are top of the evolution chain.
I agree that small variations do change (such as children from their parents) but I truely dont understand how a new species arises from this.
......... you shouldn't get hung up on the idea of different species. "Species" are, after all, just labels that humans put on different things.
Basically it usually involves a separation of the two groups, often physically. If two groups of individuals of the same species are put in two different places, such that they don't (or don't often) meet, then over many generations the small parent-to-child changes will accumulate and eventually the two groups will no longer be able to interbreed. Does that make sense to you? In some cases the groups will be subjected to selection pressures which will mean that different characteristics are favoured (say an ability to run fast and escape predators in one case, and a long nose to get food out of the ground in another), so they'll end up looking different and with different habits, but that's not really necessary for speciation.. simple random changes over time without interaction between the groups is sufficient.It's not complicated it's just that it typically takes quite a lot of generations.
Populations change over time. Given enough time and enough pressure (and things like the founder effect/bottleneck effect), these populations will become no longer able to breed with one another. We then call them new species.
Quote from: BenV on 30/03/2010 21:30:51Populations change over time. Given enough time and enough pressure (and things like the founder effect/bottleneck effect), these populations will become no longer able to breed with one another. We then call them new species.I dont understand if they are 'no longer able to breed with one another' how are they able to survive if not able to reproduce over vast periods of time? How do they quickly find an individual they can breed with?
Quote from: BenV on 30/03/2010 21:30:51......... you shouldn't get hung up on the idea of different species. "Species" are, after all, just labels that humans put on different things.Still trying to get my head around this.... what does the label 'species' refer to?
Am I right saying that if humans refained from travel and mixed race marriages then it is possible a new 'species' would evolve over time?
Quote from: echochartruse on 30/03/2010 21:58:52 Am I right saying that if humans refained from travel and mixed race marriages then it is possible a new 'species' would evolve over time?It's worth noting that "race" may not be the best indicator of genetic difference.
There's a few different definitions, but the broadest and most convenient is just two populations that cannot breed to have viable offspring.
Ah! Right, "populations" is a better term.Consider this hypothetical example.There is a population of elephants on a big island. Gradually, sea level rises, and the island becomes two island, leaving some elephants on one, and some on the other. The food supply on one island happens to favor small elephants, other way round on the other island. Over time, the two populations will differ greatly in size.Now, it's quite possible the two populations are genetically compatible, so they could possibly reintegrate. However, because they are now very different in size, interbreeding by natural means is impossible. Technically they are still a single species, but because of mutations, unless they somehow figure out a way to interbreed, over time they will become two different species.
Wouldn't it just be: each segregated group only able to breed within their group as they evolve? I dont see how this creates a separate 'species'
Birds for example, I never see them interbreeding, except for human influence or I haven't heard of it otherwise, but they are still the same species.
Why dont different 'species' interbreed? I suppose I should understand one thing before I ask another question.
Populations change over time. Given enough time and enough pressure (and things like the founder effect/bottleneck effect), these populations will become no longer able to breed with one another. We then call them new species.It honestly is that simple.
After looking back over this forum, I find that I am still confused.The word species is very confusing.
Different species/ populations cant breed together or if they do then they can not reproduce any further. But if they do and their offspring can reproduce then we call it a new species?
My interpretation of 'species' was that each group had different heritage but if we all came from the same single cell .........where did this inability to breed with each different population come into it?
A. afarensis, H. habilis, H. erectus, archaic H. sapiens, Neanderthal man and finally Cro-Magnon or modern man are all varients of the human race or are they labeled by us a different species?
...................Eventually, the two groups are genetically incompatible and labeled a new species, but eventually often takes thousands if not millions of years.The speed at which a host organism can evolve into a new species is a direct reflection of the lifespan of each generation. Since only a few mutations are "allowed" in each new generation, it takes a lot of generations to develop enough differences to prohibit reproduction with the "original" species, as well as the requirement that the two groups are completely isolated from each other.
Domestic cats are a different species than their wild counterparts, as far as I know. (Dogs, however, can interbreed with wolves and therefore aren't a separate species.) Other domesticated animals or plants might be separate species from their wild counterparts as well.
There's also a new field called synthetic life, where the goal is the creation of life (and new species) by building single-celled organisms in a lab.
After reading through this thread, I don't think the original question has been answered specifically. Darwin observed complex behavior and species/sub species differentiation due to environment ,and he described this process as 'natural selection'. He then *inferred* that this process eventually gives rise to new species. He did later work on his 'transmutation of species' again proposing that species mutate over time into new species. I have a general problem with this theory of transmutation.So, if transmutation is true, then from a critical view, there is a rather fantastic set of events that leads to a new species. We know that species are defined by their DNA that is organized into chunks, chromosomes. The the ape to man jumped happened at some point when a single individual [ape] with 48 chromosomes, mutated to a human having 46 chromosomes. At this point, that particular individual would have no one with whom he/she could successfully mate, so there must have been two...? Adam and Eve..? But a viable population must have more than just a single set of individuals to genetically propagate, it seems to me. So there was this mutation that happened to a whol large group of apes, simultaneously..?I just don't understand the mechanism of this most necessary mutation that would give rise to speciation.Anyone able to help me out here?Kevin
The genetics of speciation are extremely difficult to figure out. The reason for that is simple enough. Since speciation means that interbreeding is not possible, it becomes very hard to interbreed the different species an use the findings to determine the speciation genes. That is the opinion of Nitin Phadnis, a geneticist at the Fred Hutchinson Cancer Research Center in Seattle........"What this work shows you is that speciation can happen not only because of adaptation to the external environment, but also because of adaptation to the internal genomic environment," Phadnis says.
However, the idea that mutations are random can be regarded as untrue if one considers the fact that not all types of mutations occur with equal probability. Rather, some occur more frequently than others because they are favored by low-level biochemical reactions. These reactions are also the main reason why mutations are an inescapable property of any system that is capable of reproduction in the real world. Mutation rates are usually very low, and biological systems go to extraordinary lengths to keep them as low as possible, mostly because many mutational effects are harmful........Finally, still other sources of mutations are the many different types of transposable elements, which are small entities of DNA that possess a mechanism that permits them to move around within the genome. Some of these elements copy and paste themselves into new locations, while others use a cut-and-paste method. Such movements can disrupt existing gene functions (by insertion in the middle of another gene), activate dormant gene functions (by perfect excision from a gene that was switched off by an earlier insertion), or occasionally lead to the production of new genes (by pasting material from different genes together)......Many direct and indirect methods have been developed to help estimate rates of different types of mutations in various organisms. The main difficulty in estimating rates of mutation involves the fact that DNA changes are extremely rare events and can only be detected on a background of identical DNA.
The thrust of this presentation has been to point out how the discovery of transposable elements as agents of genome restructuring has brought the questionof evolutionary change into the realm of cell biology, where regulation and biological informationprocessing are major factors. We are entering the next century with an increasingly computational view of cells and how they make important decisions. The argument here is that evolutionary change is not exempt from this new perspective. Evidence from a variety of systems indicates that transposable elements can interact in a molecularly plausible way with signal transduction networks, the key information processing entities in the cell. Biological feedback can play a critical role in genomic responses to emergencies (McClintock, 1984). Thus, organisms have a farmore powerful evolutionary potential to generate integrated genomic networks and ensure the survival oftheir descendants than predicted by current theories of gradualism and random mutation.